Improvements in or relating to the sound-proofing of ships

ABSTRACT

This invention relates to a method of sound-proofing a ship and to a ship constructed accordingly. The noisy parts of the ship, containing the power plant, are separated from the other parts of the ship to be kept silent by a layer which is adapted to reflect sound conducted through the air and to absorb sound conducted through the solids and through this layer. Thus, it is avoided that sound is spread over parts above this layer.

Piening 1 51 se a. 25, 1973 IMPROVEMENTS IN OR RELATING TO THE SOUND-PROOFING OF SHIPS Murphy 52/480 X Stevens 52/480 X [76] Inventor: 3:31;; e1:1engegr,nll)a1rcletr1chstal 4, Bad Primary Examiner Milton Buchler y Assistant ExaminerStuart M. Goldstein [22] Filed: Apr. 12, 1971 Att0meyJohn Lezdey [21] Appl. No.: 133,118

[57] ABSTRACT [52] US. Cl. 114/85, 1 14/65 This invention relates to a method of sound-Proofing 51] Int. Cl B63b 3/52 p and to a p Constructed accordingly, The noisy [58] Field of Search 114/0.5 R, 65, 71, parts of the ship, containing the power plant, are p 1 4/7 73 74 A, 5; 244/119; 1 1 33 G, 33 rated from the other parts of the ship to be kept silent 52/48(), 404 40 24 15 22 2 35 R by a layer which is adapted to reflect sound conducted through the air and to absorb sound conducted through 5 References Cited the solids and through this layer. Thus, it is avoided that UNITED STATES PATENTS sound is spread over partsabove this layer.

1,991,675 2/1935 Hussman 114/78 10 Claims, 4 Drawing Figures PATENIEI] SEP25 I973 SHEET 1 OF 3 lnrentan Werner Pie/my PArtmmssrzsms 3.760.757

SHEET 20F 3 Fig.4

lnrenlor: Werner Piem'r IMPROVEMENTS IN OR RELATING TO THE SOUND-PROOFING OF SHIPS The invention relates to a method of sound-proofing ships.

The increasing tendency in modern ship-building to locate the power plant, the living quarters, and the bridge in the stern of the vessel results in the noisy parts of a ship being located in the immediate vicinity of parts which have to be kept quiet, so that very effective measures have to be taken in order to observe the level of sound, for example 60 dB(A) in the cabins, required by the Seamens Union.

According to the present invention, there is provided a method of sound proofing a ship in which a layer adapted to absord sound conducted through solids and to reflect sound conducted through the air is arranged only on the floor separating the part of the ship housing the power plant from the parts to be kept silent.

The invention will be described further, by way of example, with reference to the accompanying drawings in which:

FIG. 1 is a longitudinal section through a part of the ship hull sound-proofed in accordance with the prior art.

FIG. 2 is a longitudinal section through a part of a floating floor in accordance with the prior art.

FIG. 3 is a longitudinal section through a part of a sound-proofed'ship constructed in accordance with the invention.

FIG. 4 is a longitudinal section through a part of a lining having an insulating layer constructed in accordance with the invention.

The method of insulation which has been used hitherto is shown in FIGS. 1 and 2. Surfaces, adapted to absorb sound conducted through the air but without any influence on sound conducted through solids, especially the floors, are provided in the parts to be kept quiet. Surfaces 4 of this kind have been attached to the ceilings in the decks l and 2 above the engine room 3, and the entire engine room is lined with such surfaces 9. Also sprung floors 6 and 8 are provided on the floors of deck 1. Since the sound conducted through the walls and. floors remains undamped, it spreads over the whole ship. This necessarily implies that the acoustic insulation has to be dispersed over a large portion of the ship. Thus, sound-absorbent ceilings have to be arranged in the spaces in higher decks, such as deck 2.

The sprung floor has some disadvantages. As illustrated in F [6.2 for example, it comprises a sheet metal plate 8 which rests on resilient piles 10 of mineral wool and which is reinforced by angular members 12 made from sheet metal. These parts provide a vibratory system which satisfactorily reflects sound above its natural frequency. Since the vibratory energy is reflected, it flows, owing to the rigid highly conductive construction of the ship, to other places where further measures have to be taken.

A further difficulty resides in the erection of the cabin walls. If they are mounted on the deck in the manner of the walls 14, i.e., the floor 6 is arranged within the cabins, sound conducted through solidsis transmitted to the walls and radiated. If the walls are erected on the floor 8 in the manner of the wall 16, the vibratory system is disturbed and the effect of reflection is impaired. The same applies to the lateral joint of the floor which has to be of watertight construction. It

cannot be avoided to encaster the floor at its edges. This, however, leads to sound conductions at these joints.

It is therefore an object of the present invention to provide a method of sound proofing a ship which is more efficient and can be carried out by simple means. In contrast to the prior art, the layer arranged above the noisy parts of the ship is adapted to absorb sound conducted through solids. The layer is reflecting the part of the sound conducted through the air and impinging on it while it absorbs, i.e., transforms into heat that part of the sound, conducted through solids into the layer. Thus, the sound cannot penetrate through the layer according to the invention or at most to an admissible extent.

A ship hull according to the present embodiment is constructed in the following manner.

The acoustic insulation is concentrated in a layer 20 which, as illustrated in FIG. 3, is fitted in one piece across the entire area between the engine room 3 and a space 21 containing the propeller shaft on the one hand and the lower deck 1 on the other hand. The layer 20 comprises for example a sandwich arrangement of sheet metal, i.e., a composite sheet of high internal damping and a thickness which results from the flexibility to be permitted. The composite sheet is laid on supports 22 at a height of about 5 to 6 cm above the floor 24 of the deck, so that an additional insulating layer of air is provided therebetween. The supports 22 are spaced about 30 to 40 cm apart in the longitudinal and transverse directions of the ship. They contain blocks '26 which prevent the transmission of sound by increasing the impedance. Each block comprises a portion of circular or square iron with a rubber plate 28 cemented to the bottom. The softness of the rubber plate depends upon the admissible resilience of the floor. The rubber plate 28 is cemented to a plate 29.made from sheet metal of 2 mm thickness. The sheet metal plate projects laterally beyond the rubberplate and its own edges are connected to the floor 24 of the deck by spot welding. A U-shaped bracket 30 engages over each block from above. The brackets of the supports are aligned with one another with respect to their vertical position and are then secured to the blocks by welding points 32. The composite sheet 20 is secured to the brackets 30 by rivets 33. The sound waves transmitted from the relatively hard supports 22 to the damped composite sheets 20 die away rapidly with the distance from the point of origin, i.e., from the point at which the composite sheet 20 is supported on the U-shaped brackets 30 of the supports, so that the radiation of sound transmitted by air is negligible. The edge of the composite sheet 20 has welded thereto a rim which is sealed with a resilient cement, a feature which is known per se and which is therefore not illustrated.

The air layer between the floor 24 of the deck and the composite sheet 20 is slightly damped by a soundabsorbent material, particularly loose mineral wool 34, so that resonances are avoided in the air space. The cabin walls 36 are erected such that the sound path from the supports 22 to the cabin walls is as long as possible in order to prevent direct transmission of sound. The furniture in the cabins 1 is erected on the composite sheets 22 in a corresponding manner such that the points or edges of support of the furniture are at the greatest possible distance from the points of support provided by the supports 22.

Not only are the cabins 1 directly above the power plant effectively sound-proofed by the measures described above, but, due to the withholding of sound energy by the composite sheet 20, a sufficiently low level of sound also prevails in the higher decks 2, so that it is no longer necessary to take additional measures in the higher decks.

I claim:

1. A method of sound-proofing a ship having an engine room and associated noisy compartments in the lower part thereof and at least one deck thereabove comprising mounting a plurality of supports in spaced relation to each other on the upper surface of the deck immediately above the engine room and associated noisy compartments, said supports comprising metal blocks each having a rubber plate attached to the bottom of said block, and mounting on said spaced supports a sound-proofing layer to form a floor above said deck and spaced therefrom, said layer being adapted to absorb and attentuate sound conducted to it through solid members and to reflect sound striking it through the air.

2. A method as claimed in claim 16 in which the height of said supports is between about 5 and about 6 centimeters.

3. A method as claimed in claim 16 wherein the plurality of supports are mounted between about 30 and about 40 centimeters apart in both the longitudinal and transverse directions of the ship.

4. A method as claimed in claim 16 wherein said metal block is an iron block.

5. A method as claimed in claim 16 wherein each rubber plate is cemented to the bottom of its associated block, the softness of the rubber being selected according to the desired resilience of the layer mounted on said support.

6. A method as claimed in claim 20 wherein each rubber plate is cemented to a metal plate which projects laterally beyond the rubber plate and is welded to the deck.

7. A method as claimed in claim 16 wherein each support includes a U-shaped downwardly open bracket engaging the block from above, aligning said brackets with adjacent blocks and welding each bracket to its associated block.

8. A method as claimed in claim 22 wherein the top of each U-shaped bracket is riveted to the superimposed sound-proofing layer.

9. A method as claimed in claim 16 wherein cabin walls and furniture disposed on said sound-proofing layer are secured thereto at positions as far removed as possible from the points at which the layer is supported on said supports.

10. A method as claimed in claim 16 and further comprising disposing loose mineral wool in the space between the deck and the sound-proofing layer spaced therefrom. 

1. A method of sound-proofing a ship having an engine room and associated noisy compartments in the lower part thereof and at least one deck thereabove comprising mounting a plurality of supports in spaced relation to each other on the upper surface of the deck immediately above the engine room and associated noisy compartments, said supports comprising metal blocks each having a rubber plate attached to the bottom of said block, and mounting on said spaced supports a sound-proofing layer to form a floor above said deck and spaced therefrom, said layer being adapted to absorb and attentuate sound conducted to it through solid members and to reflect sound striking it through the air.
 2. A method as claimed in claim 16 in which the height of said supports is between about 5 and about 6 centimeters.
 3. A method as claimed in claim 16 wherein the plurality of supports are mounted between about 30 and about 40 centimeters apart in both the longitudinal and transverse directions of the ship.
 4. A method as claimed in claim 16 wherein said metal block is an iron block.
 5. A method as claimed in claim 16 wherein each rubber plate is cemented to the bottom of its associated block, the softness of the rubber being selected according to the desired resilience of the layer mounted on said support.
 6. A method as claimed in claim 20 wherein each rubber plate is cemented to a metal plate which projects laterally beyond the rubber plate and is welded to the deck.
 7. A method as claimed in claim 16 wherein each support includes a U-shaped downwardly open bracket engaging the block from above, aligning said brackets with adjacent blocks and welding each bracket to its associated block.
 8. A method as claimed in claim 22 wherein the top of each U-shaped bracket is riveted to the superimposed sound-proofing layer.
 9. A method as claimed in claim 16 wherein cabin walls and furniture disposed on said sound-proofing layer are secured thereto at positions as far removed as possible from the points at which the layer is supported on said supports.
 10. A method as claimed in claim 16 and further comprising disposing loose mineral wool in the space between the deck and the sound-proofing layer spaced therefrom. 